The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system Jack and Annie are on a mission to save Merlin from his sorrowsThe brother-and-sister team travel back in the magic tree house to the period known as the Renaissance. This time, Jack and Annie will need more than a research book and a magic wand. They'll need help from one of the greatest minds of all time. What will they learn from Leonardo da Vinci? Formerly numbered as Magic Tree House #38, the title of this book is now Magic Tree House Merlin Mission #10: Monday with a Mad Genius. Did you know that there's a Magic Tree House book for every kid? Magic Tree House: Adventures with Jack and Annie, perfect for readers who are just beginning chapter books Merlin Missions: More challenging adventures for the experienced reader Super Edition: A longer and more dangerous adventure Fact Trackers: Nonfiction companions to your favorite Magic Tree House adventures Have more fun with Jack and Annie at MagicTreeHouse.com